Assessing the Influence of Cumulative Chlorella vulgaris Intake on Broiler Carcass Traits, Meat Quality and Oxidative Stability

The impacts of cumulative Chlorella vulgaris intake (proportion of microalga in the diet multiplied by the total feed consumed by each bird) on broiler carcass traits, meat quality and oxidative stability were reviewed to identify the optimal intake levels for maximising benefits. Our findings indicate that a cumulative intake of 8.73 g/bird significantly enhances thigh yield, while levels ranging from 8.73 to 401 g/bird optimise carcass weight and overall meat quality. However, higher cumulative levels may reduce carcass dressing percentage due to metabolic inefficiencies. Furthermore, C. vulgaris intake improves the oxidative stability of broiler meat by increasing antioxidant levels and balancing pro- and antioxidants. Including C. vulgaris in broiler diets boosts total carotenoid content, and antioxidant assays confirm that it enhances meat oxidative stability, with low to moderate cumulative intake levels (8.73 to 401 g/bird) providing the best balance of benefits. Optimal oxidative stability and antioxidant properties were observed at a cumulative intake level of 401 g/bird, showing significant improvements in meat antioxidant capacity. Higher levels may lead to diminishing returns or potential negative effects due to the digestibility issues of the microalga. Future research should refine intake models, understand the bioavailability of C. vulgaris nutrients and explore cost-effective methods to enhance its digestibility, to ensure its viability and sustainability as a feed additive.


Introduction
Chlorella vulgaris (C.vulgaris) was first described in 1890 by Martinus Beijerinck, a distinguished microbiologist and botanist [1].With the world's population projected to reach 9.7 billion by 2050, there is an urgent need for sustainable and health-enhancing livestock feeds [2].Estimates indicate that maize and soybean, two of the main conventional feedstuffs for broiler production, will face unsustainable competition shortly due to their demand as human food, animal feed ingredients, and biofuel sources [3].This challenge has led to an increased focus on natural additives and alternative feedstocks that can improve the well-being and productivity of livestock [4,5].Microalgae have attracted considerable interest as feed supplements in poultry diets because of their potential to enhance the health and growth performance of broilers.Their nutritional benefits have made them a significant focus of research and study [6,7].
Chlorella vulgaris, in particular, is highly esteemed for its rich nutritional profile, including high concentrations of protein, vitamins (especially D and B12, which are typically acids (PUFAs).In addition, it is well known that dietary supplementation with these antioxidants can improve meat quality by reducing oxidative stress and enhancing the antioxidative capacity of the meat [30,31].
The primary objective of this review was to search major reference databases (PubMed, NCBI; Web of Science, Clarivate Analytics; Scopus, Elsevier B.V.; and Google Scholar, Google LLC, Mountain View, CA, USA) to assess the dose-response relationship between various cumulative levels of C. vulgaris intake and its effects on key broiler carcass parameters, meat quality traits and meat oxidative stability.We hypothesized that the effects observed are due to the unique transfer kinetics of C. vulgaris's bioactive compounds to the birds.Ultimately, this review aimed to identify the optimal dosage ranges of C. vulgaris that maximize broiler carcass traits, meat quality characteristics and oxidative balance.Additionally, we aimed to identify any potential thresholds beyond which C. vulgaris supplementation could provide lower outcomes or adverse effects on these key parameters.

Effects of Varying Cumulative Intake Levels of Chlorella vulgaris on the Broilers' Carcass Traits
Table 1 provides a summary of the effects of varying cumulative intake levels of C. vulgaris on several carcass traits in broilers, including carcass dressing percentage, carcass weight, thigh yield, breast meat cooking loss and water holding capacity.The cumulative intake of C. vulgaris was calculated based on the proportion of microalga in the diet and the total feed consumed by each bird.The initial weights of the broilers in the studies varied from 40.03 to 109 g, covering very young broilers (1-day-old) and older ones (21-days-old).The percentage of C. vulgaris included in the feed ranged from 0.05% to 20%, with trial durations spanning from 14 to 41 days.Consequently, cumulative alga intake varied widely, from 1.40 to 718 g/bird.Lower inclusion levels (e.g., 0.05%, 0.10%) resulted in cumulative intakes of around 1.4 to 4.35 g/bird, while higher inclusion levels (e.g., 10%, 15%, 20%) led to significantly higher cumulative intakes, ranging from 176 to 718 g/bird.These variations highlight the diverse impacts of C. vulgaris supplementation on broiler carcass traits across different studies.
Table 2 presents the results of a regression analysis aimed at predicting dependent carcass variables based on cumulative C. vulgaris intake, as compiled in Table 1.To ensure statistical reliability, the analysis included only variables with three or more degrees of freedom (dof).The data analysis was performed using SPSS software (version 29.0, 2024) and involved various regression and curve estimation techniques.These techniques are compound, cubic, exponential, growth, inverse, linear, logarithmic, logistic, power, quadratic and sigmoid models.The primary focus was on the cumulative C. vulgaris intake as the independent variable influencing broiler carcass traits, meat quality and oxidative stability.Additional data on broilers' carcass traits, for variables with less than three dof, are described in Table A1 of Appendix A.
The carcass dressing percentage, which measures the proportion of live weight resulting in the dressed carcass, showed variability with different levels of cumulative C. vulgaris intake.For instance, Cabrol et al. [10] reported the highest dressing percentage of 74.46% at a 10% inclusion level, corresponding to a cumulative intake of 401 g/bird.In contrast, lower inclusion levels such as 0.10% (4.35 g/bird) yielded a dressing percentage of 61.3% [32].The inverse model demonstrated an inverse relationship between cumulative C. vulgaris intake and carcass dressing percentage (R 2 = 0.711, p = 0.009), suggesting that as the cumulative intake of C. vulgaris increases, the carcass dressing percentage tends to decrease.The inverse model equation y = 73.444− (48.944/x) indicates that higher levels of C. vulgaris supplementation might reduce the carcass dressing percentage due to possible metabolic or digestive inefficiencies in broilers at high intake levels.This finding underscores the importance of optimizing C. vulgaris intake levels to balance benefits without exceeding the birds' physiological capacity to utilize the supplement effectively.
Carcass weight, a key measure of meat yield, showed a positive correlation with cumulative C. vulgaris intake.Broilers fed a diet with a 10% inclusion level (401 g/bird) had the highest carcass weight of 2099 g [10].Conversely, a lower cumulative intake of 6.71 g/bird (0.2% inclusion) resulted in a carcass weight of 1416 g [33].The cubic model best fits this relationship (R 2 = 0.942, p = 0.006), demonstrating a significant positive correlation.The cubic model equation y = 1457.699+ 5.041x − 0.011x 2 + 6.559 × 10 −6 x 3 suggests that initial increases in C. vulgaris intake lead to substantial gains in carcass weight, but the rate of weight gain slows down at very high levels of intake, indicating diminishing returns.This model helps identify the optimal range of C. vulgaris supplementation for maximising carcass weight without encountering a plateau effect at higher dosages.
Thigh yield, an important measure of meat quality and quantity, ranged from 25.8% to 29.6% in the studies reviewed.Abou-Zeid et al. [32] observed the highest thigh yield of 29.6% with a cumulative intake of 8.73 g/bird (0.2% inclusion).The exponential model applied to these data would suggest a consistent increase in thigh yield with higher cumulative C. vulgaris intake, as indicated by the model's significant correlation (R 2 = 0.961, p = 0.003).However, the simplified equation, y = 29.195,implies that the exponential model predicts a constant thigh yield value of 29.195, regardless of the cumulative value of C. vulgaris intake.This reflects the supplement's positive impact on muscle deposition, particularly in the thighs, making C. vulgaris a valuable additive for improving meat quality and quantity.
Breast meat cooking loss, an important indicator of meat quality, showed variation with different levels of C. vulgaris intake.Lower cooking loss percentages, which are desirable for meat quality, were observed with moderate inclusion levels, such as 12.6% at a cumulative intake of 3.52 g/bird [34].However, the cubic model used to analyse this relationship (R 2 = 0.252, p = 0.539) suggests a weak and statistically insignificant correlation.The cubic model equation y = 22.129 − 0.001x + 7.794 × 10 −5 x 2 − 1.028 × 10 −7 x 3 indicates that while there is some variation in cooking loss with changes in C. vulgaris intake, this trait is likely influenced by other factors beyond C. vulgaris supplementation.The low R 2 value and high p-value suggest that factors such as genetics, overall diet composition and environmental conditions may also play significant roles in determining breast meat cooking loss.
Water holding capacity (WHC), a crucial quality trait that affects meat juiciness and texture, showed improvement with higher levels of C. vulgaris intake.The highest WHC recorded was 88.33% at a cumulative intake of 20.0 g/bird (0.60% inclusion) [33].The relationship between cumulative C. vulgaris intake and WHC is best described by a sigmoid model, suggesting a positive trend.The model equation y = 4.435 − (0.329/x) describes an S-shaped curve, indicating that WHC improves gradually with increasing C. vulgaris intake up to a certain point before levelling off.The R 2 value of 0.311 and p-value of 0.193 indicate a non-significant correlation, suggesting that while there is a positive trend, other factors may also influence WHC.This S-shaped trend highlights the importance of identifying an optimal range of C. vulgaris supplementation that maximizes WHC without incurring unnecessary costs or potential negative effects associated with excessive intake.
Overall, these findings demonstrate that cumulative C. vulgaris intake significantly influences broiler carcass traits, with optimal intake levels crucial for maximising benefits.Inclusion levels of 0.2% (8.73 g/bird) enhance thigh yield, while 0.2% to 10% (ranging from 8.73 to 401 g/bird) optimise carcass weight and meat quality.For instance, a 0.10% inclusion (4.35 g/bird) yields a dressing percentage of 61.3%, whereas 10% (401 g/bird) results in a higher carcass weight of 2099 g.However, higher levels (e.g., 20%, 718 g/bird) may reduce carcass dressing percentage due to metabolic inefficiencies.Further research is necessary to refine intake models and understand the bioavailability of C. vulgaris nutrients, focusing on its bioactive compounds' impact on broiler metabolism and health.This will help identify the optimal C. vulgaris intake levels for enhancing carcass traits and meat quality in broiler production, ensuring both efficiency and efficacy in its use as a feed additive.

Effects of Varying Cumulative Intake Levels of Chlorella vulgaris on the Broilers' Meat Quality and Oxidative Stability
The microalga C. vulgaris has the potential to enhance meat quality by increasing levels of lipid-soluble antioxidant vitamins.These vitamins include vitamin E homologues (tocopherols and tocotrienols) and vitamin A, along with its precursors, such as certain carotenoids like β-carotene [36].
Table 5 presents a comprehensive summary of the regression analysis performed using SPSS software (version 29.0, 2024) to predict dependent variables associated with meat quality traits and oxidative stability, considering the cumulative intake of C. vulgaris.This analysis integrates data from Tables 3 and 4, offering insights into how cumulative consumption of C. vulgaris influences these specific meat quality parameters and oxidative stability measures.To ensure statistical reliability, only variables with three or more dof were included in the analysis.Data were analysed as described before for carcass trait variables, using the cumulative intake of C. vulgaris as the independent variable influencing various meat variables metrics.The table details the best-fitting model type, R-square values, dof, p-values and the model equations for each variable.Data on broilers' meat quality for variables with less than three dof are provided in Table A2 of Appendix A.
The breast meat pH24h, which indicates the acidity level of the meat and can influence meat quality and shelf life, varied with different levels of C. vulgaris intake.For instance, An et al. [35] reported a pH24h of 5.68 at a cumulative intake of 14.1 g/bird (0.50% inclusion), while higher inclusion levels such as 0.60% (20.0 g/bird) yielded a pH24h of 6.603 [30].The regression analysis in Table 5 utilizes a sigmoid model (R 2 = 0.163, p = 0.219), indicating a non-significant correlation between cumulative C. vulgaris intake and pH24h.The model equation y = 1.817 − (0.111)/x suggests a slight decrease in pH24h as C. vulgaris intake increases.However, the weak correlation implies that other factors significantly influence meat pH beyond C. vulgaris intake.
The lightness (L*) of breast meat, which measures the brightness of the meat, varied with different levels of C. vulgaris intake.For example, An et al. [32] reported the highest lightness value of 60.3 at a cumulative intake of 1.40 g/bird (0.05% inclusion).In contrast, a cumulative intake of 401 g/bird (10% inclusion) yielded a lightness value of 54.63 [6].The cubic model (R 2 = 0.909, p = 0.046) suggests a significant relationship between cumulative C. vulgaris intake and meat lightness.The model equation y = 60.123− 0.163x + 0.001x 2 − 4.626 × 10 −7 x 3 indicates that lightness decreases with increasing C. vulgaris intake initially but can stabilize or even improve slightly at higher levels, reflecting the complexity of C. vulgaris's impact on meat colour. 1 Slaughtering day was not considered for this calculation. 2Percentage of microalgae in the diet multiplied by the total feed ingested per animal during the experiment.If cumulative feed intake (CFI) results were not available, the following estimation was made: CFI (g/bird) [10] = CFI (g/pen)/number of birds; CFI (g/bird) [18] = CFI (g/d/pen) × number of trial days/ number of birds; CFI (g/bird) [34] = CFI (g/d/bird) × number of trial days. 3For Cabrol et al. [10], the estimation of total carotenoids (µg/100 g) was determined considering an average of 25% dry matter on breast meat. 4Fatty acids: ALA-alpha-linolenic acid; DHA-docosahexaenoic acid; DPA-docosapentaenoic acid; EPA-eicosapentaenoic acid; LA-linoleic acid; PUFA-polyunsaturated fatty acids. 5DPPH free RSA (mg GAE/100 g DW)-the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) measures the antioxidant properties, using free radicals for assessing the potential of substances to serve as hydrogen providers or free radical scavengers (FRS), expressed in mg of gallic acid equivalents (GAE) per 100 g of dry matter. 6FRAP test (mg GAE/100 g DW)-Ferric reducing antioxidant power (FRAP) assay, expressed in mg of gallic acid equivalents (GAE) per 100 g of dry matter. 7TPC (mg GAE/100 g DW)-Total phenolic content (TPC), expressed in mg of gallic acid equivalents (GAE) per 100 g of dry matter. 8Male broilers. 9Female broilers.
Foods 2024, 13, 2753 10 of 17 quality.Higher levels may lead to diminishing returns or potential negative effects.Moreover, optimal oxidative stability and antioxidant properties were observed at cumulative intake levels around 10% inclusion (401 g/bird), showing significant improvements in meat antioxidant capacity.This suggests that careful management of C. vulgaris intake can optimize broiler meat quality by leveraging its antioxidant potential.The redness (a*) of breast meat, which indicates the intensity of the red colour and is often associated with fresh meat quality, varied with different levels of C. vulgaris intake.Alfaia et al. [18] observed the highest redness value of 4.45 at a cumulative intake of 176 g/bird (10% inclusion).In contrast, lower inclusion levels, such as 0.15% (4.27 g/bird), resulted in a redness value of 0.57 [35].The cubic model (R 2 = 0.867, p = 0.079) suggests a tendential relationship between cumulative C. vulgaris intake and meat redness.The model equation y = 0.701 + 0.039x + 0.000x 2 + 1.096 × 10 −7 x 3 indicates that redness increases with higher C. vulgaris intake.

Degrees of Freedom
The yellowness (b*) of breast meat, which measures the intensity of the yellow colour and can significantly affect consumer perception, varied with different levels of C. vulgaris intake.Cabrol et al. [10] reported the highest yellowness value of 20.14 at a cumulative intake of 561 g/bird (15% inclusion).In contrast, a cumulative intake of 1.40 g/bird (0.05% inclusion) resulted in a yellowness value of 7.89 [35].The cubic model (R 2 = 0.998, p < 0.001) demonstrates a significant relationship between cumulative C. vulgaris intake and meat yellowness.The model equation y = 7.963 − 0.004x − 1.228 × 10 −7 x 3 suggests that yellowness increases with higher C. vulgaris intake, indicating a substantial impact of the microalga on this colour trait.
Total carotenoid content in broiler breast meat, crucial for nutritional quality and antioxidant properties, showed a significant variation with different levels of C. vulgaris intake.The sigmoid model (R 2 = 0.983, p = 0.008) suggests a significant relationship, with the model equation y = 7.922 − (458.036/x).This indicates a sharp increase in carotenoid content at lower C. vulgaris levels, plateauing at higher intakes.Despite the strong correlation, the limited number of dof (2) suggests caution is required in interpreting these results.
Regarding pro-oxidant fatty acids, LA, an essential n-6 PUFA, is critical for broiler meat quality.The sigmoid model (R 2 = 0.730, p = 0.065) indicates a tendential significant correlation between C. vulgaris intake and LA content, with the model equation y = 3.323 − (1.701/x).LA content increases initially with C. vulgaris intake but levels off at higher levels.ALA, an n-3 PUFA, showed a non-significant correlation with cumulative C. vulgaris microalga intake.The sigmoid model (R 2 = 0.310, p = 0.330) and the model equation y = 0.424 + (0.437/x) suggest a minimal increase in ALA content with lower C. vulgaris intake.The relationship is not statistically significant, indicating that random factors may largely influence ALA content.EPA, an n-3 PUFA known for its health benefits, showed a significant inverse relationship with C. vulgaris intake.The inverse model (R 2 = 0.951, p = 0.005) and the model equation y = 0.205 + (2.693/x) indicate that EPA content decreases with increasing C. vulgaris intake.DPA, another n-3 PUFA, exhibited a significant exponential decrease with increasing C. vulgaris intake.The exponential model (R 2 = 0.917, p = 0.043) and the model equation y = 0.500•e −0.002x confirm this trend.However, the limited number of dof (2) suggests careful interpretation is necessary.DHA, an n-3 PUFA crucial for brain and heart health, showed a non-significant correlation with C. vulgaris intake.The logarithmic model (R 2 = 0.176, p = 0.481) and the model equation y = −2.942+ 0.622lnx suggest a slight increase in DHA content with higher C. vulgaris intake, but the relationship is not statistically significant.Total PUFA content, essential for health benefits, showed a significant relationship with C. vulgaris intake.The sigmoid model (R 2 = 0.963, p = 0.003) and the model equation y = 3.693 − (1.943/x) indicate a significant increase in PUFA content with increasing C. vulgaris intake, which levels off at higher intakes.
The antioxidant properties of C. vulgaris in broiler meat were evaluated using the DPPH assay, which measures the antioxidant capacity by evaluating free radical scavenging activity.El-Bahr et al. [34] reported a DPPH-free RSA of 17.11% at a cumulative intake of 3.52 g/bird (0.10% inclusion).At a much higher intake of 176 g/bird (10% inclusion), Alfaia et al. [18] observed a DPPH-free RSA of 25.8%.Further increasing the cumulative intake to 561 g/bird (15% inclusion) resulted in a DPPH-free RSA of 28.609%, with a slight decrease to 23.537% at 718 g/bird (20% inclusion) [6].
In addition to the DPPH assay, the FRAP assay, which measures the reducing power, showed that FRAP values increased with higher C. vulgaris intake.Cabrol et al. [10] reported FRAP values of 287.3 mg of gallic acid equivalents (GAE)/100 g of dry weight (DW) at 401 g/bird (10% inclusion), 414.09 mg GAE/100 g DW at 561 g/bird (15% inclusion) and 405.97 mg GAE/100 g DW at 718 g/bird (20% inclusion).Furthermore, TPC, known for its antioxidant properties, was also influenced by C. vulgaris intake.The same authors reported TPC values of 153.3 mg GAE/100 g DW at 401 g/bird (10% inclusion), 174.7 mg GAE/100 g DW at 561 g/bird (15% inclusion) and 174.3 mg GAE/100 g DW at 718 g/bird (20% inclusion).Overall, cumulative C. vulgaris intake enhances the oxidative stability of broiler meat by increasing antioxidant levels and balancing pro-and antioxidants.The inclusion of C. vulgaris in broiler diets boosts total carotenoid content, which protects meat from oxidative damage and improves shelf life and nutritional quality.Antioxidant assays (DPPH, FRAP and TPC) confirm that C. vulgaris enhances meat oxidative stability, although there is a threshold beyond which no additional benefits are observed.Data indicate that low to moderate inclusion levels of C. vulgaris (0.2% to 10%, or 8.73 to 401 g/bird) generally provide the best balance of benefits for oxidative stability and meat quality.Higher levels may lead to diminishing returns or potential negative effects.Moreover, optimal oxidative stability and antioxidant properties were observed at cumulative intake levels around 10% inclusion (401 g/bird), showing significant improvements in meat antioxidant capacity.This suggests that careful management of C. vulgaris intake can optimize broiler meat quality by leveraging its antioxidant potential.

Safety and Regulations
Several important considerations emerge when evaluating the safety precautions and regulatory aspects of using C. vulgaris when used as a feed additive or ingredient in broiler feeding.It is imperative that dietary C. vulgaris is safe, particularly when it is controlled for contaminants.Regulatory authorities like the European Food Safety Authority (EFSA) and the U.S. Food and Drug Administration (FDA) generally recognize C. vulgaris as safe, provided it is produced and processed under strict quality control measures.
Research suggests that contaminants from freshwater sources in C. vulgaris are typically present at amounts below detectable thresholds, reinforcing its safety profile.Ensuring that C. vulgaris is free from contaminants like toxic metals or pathogenic microorganisms is crucial, as these can pose significant health risks to both poultry and consumers.The possibility of bioaccumulation of these contaminants in broiler tissues, especially at higher levels of C. vulgaris intake, requires demanding and regular safety assessments.This underscores the requirement for well-established safety protocols in the industrial production and processing of C. vulgaris for animal feed.Ensuring proper cultivation and production conditions can keep contaminant levels, such as heavy metals and harmful microorganisms, within acceptable limits [37].Maintaining the safety of C. vulgaris as a feed additive requires strict adherence to quality control measures, including regular toxicity analyses and monitoring of microcystin levels.
The regulatory framework for using C. vulgaris microalga in animal feed is complex and varies across different regions [38,39].Adherence to local and international regulations concerning feed safety, allowable additive levels and labelling requirements is essential [40,41].These regulations are designed to ensure the safety of animal feed additives and, consequently, the safety of animal-derived food products for human consumption.Regulatory standards are often updated based on new scientific discoveries and public health considerations.Ongoing research adds to a growing body of evidence that may inform regulators in revising and updating guidelines for the use of C. vulgaris in poultry diets.
Further investigation is needed to determine the long-term safety of C. vulgaris, especially when used at high incorporation levels and over extended feeding periods.Although short-term studies indicate beneficial effects, the long-term consequences for both animal and human health are not yet fully understood.This gap in knowledge underscores the necessity for ongoing research and monitoring to detect any potential adverse effects, including the cumulative effect of bioactive components in C. vulgaris on the health of animals and the safety of food.
Summing up, although C. vulgaris microalga provides notable health advantages as a poultry feed additive, its safe integration into broiler diets requires a holistic strategy.This strategy must include stringent quality control, compliance with emerging regulatory standards and continuous research into its long-term safety and effectiveness.These measures are crucial to guarantee that broiler meat enhanced with C. vulgaris is not only advantageous but also safe and in line with regulatory requirements, thereby sustaining consumer confidence and market sustainability.

Conclusions and Future Perspectives
In conclusion, these findings demonstrate that cumulative C. vulgaris intake significantly influences broiler carcass traits, meat quality and oxidative stability, with specific optimal intake levels maximising benefits.For carcass parameters and meat quality, cumulative intake levels of 8.73 g/bird enhance thigh yield, while levels ranging from 8.73 to 401 g/bird optimise carcass weight and overall meat quality.However, higher cumulative levels, such as 718 g/bird, may decrease the carcass dressing percentage due to metabolic inefficiencies.
In addition, cumulative C. vulgaris intake enhances the oxidative stability of broiler meat by increasing antioxidant levels and balancing pro-and antioxidants.The inclusion of C. vulgaris in broiler diets boosts total carotenoid content, protecting meat from oxidative damage and improving shelf life and nutritional quality.Antioxidant assays confirm that C. vulgaris enhances meat oxidative stability, with low to moderate cumulative intake levels from 8.73 to 401 g/bird providing the best balance of benefits.Optimal oxidative stability and antioxidant properties were observed around a cumulative intake level of 401 g/bird, showing significant improvements in meat antioxidant capacity.Higher levels may lead to diminishing returns or potential negative effects, likely due to indigestibility issues.
Future research should focus on refining intake models and understanding the bioavailability of C. vulgaris nutrients, particularly the impact of its bioactive compounds on broiler metabolism and health.This will help identify optimal intake levels that enhance carcass traits and meat quality.Additionally, studies should address the variability in optimal inclusion levels and potential adverse effects at higher doses, providing precise dosing guidelines.Long-term studies are necessary to assess the sustained effects of C. vulgaris on broiler health and productivity while elucidating the mechanisms through which its bioactive compounds influence growth performance, immune response and antioxidant capacity.Exploring cost-effective methods to enhance C. vulgaris digestibility, such as mechanical disruption, enzymatic treatment and fermentation, will further optimize its use in broiler production, ensuring its viability and sustainability as a feed additive.

Table 1 .
Effects of varying cumulative intake levels of Chlorella vulgaris on the carcass traits of broilers.

Table 3 .
Effects of varying cumulative intake levels of Chlorella vulgaris on meat quality traits of broilers.

Table 4 .
Effects of varying cumulative intake levels of Chlorella vulgaris on antioxidant and pro-oxidant compounds, and oxidative stability indicators in the broiler breast meat.

Table 5 .
Summary of regression models predicting dependent meat quality traits and anti-and prooxidative compounds from cumulative Chlorella vulgaris intake.fromoxidative damage and improves shelf life and nutritional quality.Antioxidant assays (DPPH, FRAP and TPC) confirm that C. vulgaris enhances meat oxidative stability, although there is a threshold beyond which no additional benefits are observed.Data indicate that low to moderate inclusion levels of C. vulgaris (0.2% to 10%, or 8.73 to 401 g/bird) generally provide the best balance of benefits for oxidative stability and meat quality.Higher levels may lead to diminishing returns or potential negative effects.Moreover, optimal oxidative stability and antioxidant properties were observed at cumulative intake levels around 10% inclusion (401 g/bird), showing significant improvements in meat antioxidant capacity.This suggests that careful management of C. vulgaris intake can optimize broiler meat quality by leveraging its antioxidant potential.

Table 5 .
Summary of regression models predicting dependent meat quality traits and anti-and prooxidative compounds from cumulative Chlorella vulgaris intake.Fatty acids: ALA-alpha-linolenic acid; DHA-docosahexaenoic acid; DPA-docosapentaenoic acid; EPA-eicosapentaenoic acid; LA-linoleic acid; PUFA-polyunsaturated fatty acids.(20%inclusion).Overall, cumulative C. vulgaris intake enhances the oxidative stability of broiler meat by increasing antioxidant levels and balancing pro-and antioxidants.The inclusion of C. vulgaris in broiler diets boosts total carotenoid content, which protects meat from oxidative damage and improves shelf life and nutritional quality.Antioxidant assays (DPPH, FRAP and TPC) confirm that C. vulgaris enhances meat oxidative stability, although there is a threshold beyond which no additional benefits are observed.Data indicate that low to moderate inclusion levels of C. vulgaris (0.2% to 10%, or 8.73 to 401 g/bird) generally provide the best balance of benefits for oxidative stability and meat quality.Higher levels may lead to diminishing returns or potential negative effects.Moreover, optimal oxidative stability and antioxidant properties were observed at cumulative intake levels around 10% inclusion (401 g/bird), showing significant improvements in meat antioxidant capacity.This suggests that careful management of C. vulgaris intake can optimize broiler meat quality by leveraging its antioxidant potential.

Table 5 .
Summary of regression models predicting dependent meat quality traits and anti-and prooxidative compounds from cumulative Chlorella vulgaris intake.